Gyroscopes are inertial sensors for orientation, stable control and navigation. Because of bulkiness and expensiveness, the traditional gyroscope is hard to be widely used. The advanced MEMS (Mirco Electro Mechanical System) technology has greatly favored the design and fabrication of MEMS gyroscopes in the recent years. The emerging MEMS gyroscopes have been extensively applied to electronic products, such as game machines, 3D mice, image stabilization systems of video cameras, navigation systems of vehicles and the like.
The fabrication process of the MEMS gyroscopes includes many steps. The steps inevitably cause some imperfections. The imperfections include mechanical structure imperfections (such as structural asymmetry and dimensional errors) and circuit imperfections (such as parasitic capacitors). Because of miniaturization of electro mechanical components, tolerance for the imperfections is greatly reduced in MEMS systems, and the imperfections are especially significant in MEMS systems. The present invention intends to compensate for the mechanical imperfections caused by design and fabrication of the electro mechanical components and reduce the instability of the dynamics so as to correctly estimate angular velocities.
In the conventional technology, in order to enhance the performance of the gyroscopes, especially the mechanical imperfections significantly affecting the precision of MEMS devices, post-processes are usually used to perform correction. However, such a prior art is complicated and expensive, and has high technical threshold. There are also few methods using feedback control to offset the effect caused by mechanical imperfections in gyroscopes to obtain correct angular velocities. These methods generally are applied to two-axes-control-input gyroscopes. However, most of the commercial MEMS gyroscopes use single-axis-control-input and thus cannot be corrected by those existing feedback control methods.
An U.S. Pat. No. 6,928,874 disclosed “Dynamically Amplified Micro-Machined Vibratory Angle Measuring Gyroscopes, Micro-Machined Inertial Sensors and Method of Operation for the Same”, which adopts a two-axes-control-input gyroscope to replace a ring structure with an inner ring and an outer ring to reduce the interference between two axes. However, the mechanical structure of the prior art is very complicated. Besides, the prior art has to measure positions and velocities of the two axes at the same time. An U.S. Pat. No. 6,934,660 disclosed a “Multi Stage Control Architecture for Error Suppression in Micro-Machined Gyroscopes”, which designs a two-stage controller. The prior art is based on hypotheses that the damping coefficient of the gyroscope is symmetric and there is no coupling term existing. However, the hypotheses are too impractical. Similar to the above-mentioned patent, this prior art also adopts two-axes-control-input and thus has to measure positions and velocities of the two axes at the same time.